None
Not Applicable
Not Applicable
The present invention is directed to the field of humidity monitoring devices.
Humidity, or the level of moisture in an environment, is a critical concern for many applications. There are many systems and materials that can be damaged by the presence of water. Accordingly, it is important to have a method to determine the presence of moisture and even small quantities of water vapor at varying levels of humidity. Additionally, many piping systems contain fluids, principally composed of water, that have a deleterious effect on the piping system itself or on other components or materials external to such a system.
Very often, in a fluid containing system, the corrosive fluid in the system is water. Even in small quantities, due to its formation as a vapor, water can lead to corrosive effects. Water presents a great threat to most forms of carbon steel and some other metal surfaces by increasing surface corrosion. Moisture can negatively affect various chemical, mechanical, and electronic processes and components, as well as the operation of some forms of equipment, if allowed to reach sufficient levels. Even low moisture levels can produce substantial damage. In worst-case examples, where there is a high humidity condition, over a sufficiently long duration, valuable product, processes, and equipment can be destroyed, or rendered useless.
Water is a component of a corroding system and will have a continual action on materials meant to contain it. At other times, ambient moisture needs to be prevented from reaching into a sensitive area.
The present invention provides a method of indicating, as part of a monitoring system, that water has escaped from its containment system or that water has entered a moisture sensitive area.
Monitoring the humidity level in such environments therefore becomes of great concern to both manufacturers and users of such humidity sensitive products and equipment. As a result, various methods of indicating humidity exist, both electronic and chemical.
In developing a humidity sensor, it is important that such a sensor be flexible in its application, error-free (such as avoiding false negative responses), persistent, unequivocal, simple in design and inexpensive to manufacture.
In use to detect the entry of moisture, the present invention may be in the form of a self-contained unit that can be placed in view inside a sensitive area. If it is not possible to have the unit in view, it may need to be incorporated within the walls containing the sensitive components. In such a case, a viewing window would be part of the detection unit. In piping systems, the present indicator invention would typically be part of a fitting mounted into the walls of the pipe.
U.S. Pat. No. 6,131,433 to the author of the present invention (Duncan) describes a corrosion monitoring device and more particularly to a self contained, disposable corrosion monitor for a fluid containing system, which indicates a breakthrough of the integrity of the wall of the system due to the corrosive action of a fluid in the fluid containing system. More particularly, the present invention may be incorporated to provide the indication that water has broken through, when used in a system where the fluid contains water.
Failures of metal pipes, tanks and other fluid enclosures due to the deterioration of their inner wall surfaces are all too common occurrences; currently causing over 10 billion dollars annually in replacement costs alone. While some corrosion induced metal failures may create a great and unexpected financial loss due to replacement cost, down time and water damage, more severe failures of high temperature and high pressure pipes and vessels may result in explosion, extensive physical damage, severe injury and human casualty. Effective corrosion monitoring is therefore greatly desired from such a production, health, environmental, process reliability, economic and liability viewpoint.
Corrosion of metal surfaces is a continuous and generally non-stoppable electrochemical process, which is well known and documented. Given sufficient time, metal failures are inevitable where fluids and metal meet and interact, and where at best, the negative physical effects of corrosion can only be minimized, not eliminated.
Due to the complex interaction of chemical, electrical and mechanical influences which determine the degree of activity of a corrosion environment, and the fact that such corrosion activity often widely varies at different locations within the same fluid environment, there is the need to monitor as many individual locations in a given piping system, tank, pressure vessel or reactor vessel as possible. The inability to monitor the corrosion activity at multiple locations within a piping system is frequently a cause of failure, since a single monitoring point,not representative of the corrosion in the entire piping system, may produce an erroneous prediction of service life and service failure.
Chemical and electrical corrosion inhibitors and other substances exist to help reduce corrosion and are often relied upon exclusively to safeguard piping and other metal components. The use of such corrosion inhibitors does not preclude the need for corrosion monitoring, however, since actual results of anti-corrosion agents vary widely, thereby making it necessary to regularly verify their efficiency and proper application.
A wide variety of corrosion monitors and procedures exist in the literature and in current use with the purpose of measuring the corrosive nature of a fluid or fluid stream against a specific metal surface. These devices are described in U.S. Pat. No. 6,131,433, incorporated herein by reference. Many monitoring devices, therefore, find limited actual field use, provide unsatisfactory corrosion monitoring coverage due to the limited number of sensors or probes installed and provide little benefit to all but the most critical of applications.
Ultrasonic testing is well recognized for providing extremely accurate remaining wall thickness measurements for any metal structure, but typically serves as a survey or an instantaneous measuring tool rather than a long term monitoring device. It has a disadvantage of being a temporary measurement instrument, is expensive, and requires an experienced operator and careful analysis and manipulation of the resulting data, as well as periodic access to the exact same area of the pipe surface for reevaluation.
Current humidity indicators work on the basis of some chemical change occurring within a viewable material to produce a color change within that same material. Materials commonly used are based around some form of silica gel or clay or cobalt chloride. Some materials exist just as indicators of moisture, while others provide a desiccating service and also change color only after their ability to absorb moisture has been exceeded, and moisture level increases. Prior art humidity indicators vary depending upon the physical shape and differentiation in indicating ability, such as providing indication in 10% or 20% increments, although they all operate on a basic color change within a chemical compound given a certain humidity level.
The disadvantage of such indicators is that they produce a very faint color change typically varying from a light blue when new and completely dry to a faint pink or lavender when they absorb moisture. Some products offer a mildly stronger color change, or different beginning and final colors. Because the colors are faint and the change is minimal, it would not be immediately noticeable in an industrial environment without some form of prompting to view it closely. It would be unlikely to see such a color change from more than 10 feet away.
A further disadvantage of such products is that, if encountering an actual water condition and not simply a high degree of humidity, they will typically dissolve their color into the solution, or solubilize their indicator, and soon lose all potential to produce any warning. This is especially true for dye indicators that activate or react with moisture to produce their indication initially.
Therefore, if the color change were not seen within a certain period of time, it might wash out to provide no indication whatsoever and actually produce a false negative and allow a potentially dangerous condition to go unnoticed. Various applications exist where a high humidity level may precede the entry of water or a flow of water into an area, and therefore the ability of an indicator to retain its color becomes a critical feature.
U.S. Pat. No. 2,249,867 to Snelling uses a deliquescent chemical to attract water into itself so that the water can then produce a chemical color reaction within a second material adjacent to it, with the second material producing the actual color change. The colored material is described as a water-soluble dye which is activated to bring a color change after contact with water produced from the deliquescent material. That colored mixture of dye and moisture produced by the deliquescent material is then carried through a porous membrane, which previously obscured view of the chemical dye, thus producing a visual indication. Varying the deliquescent compounds used determines the point at which the deliquescent chemical begins absorbing moisture, thus producing an indication at different humidity levels.
This device, described in U.S. Pat. No. 2,249,867 to Snelling, operates on the principle of a chemical color change, does not produce a high intensity color indication, and does not employ a fixed and non-reversing color indicator. Since water contact with the dye indicator initiates the indicating reaction and allows the color to seep through the porous medium, submersion in water would dissolve and disperse the dye and therefore render the indicator useless. U.S. Pat. No. 2,214,354 to Snelling is an earlier form of the above patent.
U.S. Pat. No. 3,675,654 to Baker et al. also uses a water-soluble dye as the indicator. It is intended as a moisture indicator for diapers or other personal hygiene items to signal the need for changing. When moisture reacts with the dye, it produces a color change which then transmits through another layer of cloth or material to signal a wetness condition at the outside of the item. This invention lacks high visibility indication and may wash out in an excess of liquid.
U.S. Pat. No. 5,224,373 to Williams et al. is a humidity sensor requiring three layers of material and is based upon a chemically-treated material that changes color in response to various humidity levels present. The indicating layer undergoes a chemical change in response to moisture that has passed through a water permeable layer. Various compositions of the materials provide indication at different humidity levels.
This device does not provide a high intensity indication and is intended for providing a flexible indicator suitable for packaging of materials. As the chemical cobalt chloride is used, an excess of water would dissolve out the cobalt chloride, causing the indicator to lose its color indication and it would be rendered useless in such potential applications.
U.S. Pat. No. 5,780,721 to Levens describes a device that is intended for the detection of chemical leaks at pipeline connections, flanges, and welds, which exists as a ring clamped or fastened around a pipe joint. This patent uses foam as its principal component, which foam is selected to dissolve in response to the presence of specific organic chemicals existing within the pipeline and leaking at adjoint or seam. After the foam dissolves away or becomes transparent, the foam reveals a pre-existing visual indicator, thus producing a warning of a chemical leak.
The method of operation of the foam is that it is applied externally, particularly to detect leakage of organic compounds. It is not self-contained and can be dissolved or broken away by other external factors unrelated to any leak. It cannot attract the organic compound and requires actual contact by the organic compound, which must migrate to it.
As described, the prior art fails to disclose a device or method suitable for monitoring humidity, that is highly visible, of high intensity, non-reversible, persistent and not susceptible to false negative responses.
The present invention is a simple means for producing a highly visible, high intensity, warning indication when a certain degree of humidity exists in an area. The indication is non-reversible, cannot be lost or washed away if submerged in a liquid environment, and can accommodate a change from most colors to any other known color.
This humidity indicator may be used as a component of a corrosion monitor, such as that described in U.S. Pat. No. 6,131,433 to the author of the present invention (Duncan), which is incorporated herein by reference.
It is an object of the present invention to provide a brilliant visual indication not dependent upon a chemical color change, in which the color change can be to any color, tone or intensity desired. The color change of the present invention is readily discernible from distances of at least 40 feet away.
It is an object of the present invention to provide a humidity monitor using an indicator made from paint, epoxy, heat-bonded high temperature vinyl or any other material of color.
It is a further object of the present invention that it can be fabricated by simple means from safe, abundant materials.
It is still a further object that the color change of the present invention will not wash out or dissolve due to saturation in the liquid environment, and will remain to provide indication of a problem condition without the fear that noticeability of the indication will be lost if not immediately observed.
It is also an object of the present invention that it is simple in design, low in cost, easy to manufacture, and is easily adapted to various physical forms.
It is still another object of the present invention to provide a humidity monitor that can be used in any location and thus, along with its low cost, it will provide a benefit by allowing the monitoring of a greater number of areas of concern.
Still a further object of the present invention is that it cannot produce a false negative indication.
An object of the present invention is to provide an indication or signal, as part of a corrosion monitoring system, to owners and operators of any pipe, tank, pressure vessel, reaction vessel or other water containment or transmission system that a breakthrough of the containment surface has occurred.
Still a further object of the present invention is its use as a component of a disposable, self contained, stand alone device not requiring any further evaluation, energy, information processing, handling, maintenance or testing in order to produce an indication of the presence of humidity.
Still an additional object of the present invention is to provide an indicator for a corrosion monitor that can be tailored to meet any varying monitoring needs due to the various types of piping and material carrying systems operating under even more varying environmental conditions.
By reviewing and considering the drawings and descriptions further objects and advantages of the instant invention will be apparent.
The present invention is a device for monitoring humidity, comprising a first layer comprising a visual indicator, a second layer covering and obscuring said first layer, said second layer comprising a deliquescent material, wherein, as said deliquescent material picks up moisture and dissolves itself in said moisture, it becomes transparent exposing said first layer, a viewing means disposed on the opposite side of said second layer from the first layer, and an enclosure with an entrance for moisture containing the said first and second layers and the viewing means.